This invention relates to the formation of large-scale, continuous fiber-reinforced plastic (FRP) sheets and more particularly relates to the formation and application of such sheets to a terrain surface for the purpose of preventing moisture from seeping into the terrain. The invention also contemplates an apparatus for the on-site fabrication and installation of the plastic sheets.
In certain situations it is sometimes desirable to prevent the seepage of moisture into the ground in certain defined areas. An example of such a situation is in a irrigation system where the water is carried through fields in a shallow canal. In order to maintain a constant flow of water in the canal without excess seepage into the canal walls it has been standard practice to line the canals with concrete. While the concrete liners are effective in reducing the water seepage into the ground, it has been found that after a few years the concrete liners tend to deteriorate, particularly in cold climates which freeze during the winter. Frost heave caused by the freezing and thawing of the ground beneath the concrete liner causes cracks in the concrete and, once the cracks form, water seeping into the cracks freezes and thaws, exaggerating the cracks until it reaches the point where large sections of the canal lining will change position relative to an adjacent section so that water running through the canal will become agitated by the passage over the uneven surface. Also, seepage through the cracks in the concrete can cause the loss of a large amount of water from the beginning to the end of the canal. In an canal of any significant length, the water loss through seepage can be up to 50%.
Typically, using current methods, once the concrete has deteriorated to a point where it is seriously affecting water flow, it is necessary to refurbish the canal by removing the old concrete lining and pouring a new concrete liner in the canal. The cost of the refurbishment operation is usually greater than the initial installation cost because of the cost to remove the old concrete prior to pouring a new concrete liner. Attempts have also been made to line the canals by laying a relatively thick film of flexible water-impermeable material such as, polyethylene or vinyl, in the canal. One problem that has been discovered with use of such thick polyethylene or vinyl film is that if a significant amount of water at typical velocity is channeled down the canal it will tend to drag the film with it, causing wrinkling of the film, which, again, changes the water flow characteristics. In other instances the film is covered with dirt and coarse gravel, also decreasing the efficiency of operation of the canal system. Also, since the canals are in agricultural environments it is not unusual for livestock to walk in the canal. The polyethylene film is easily damaged by the hooves of the livestock, as well as by covering with dirt and rock and during installation.
It is therefore an object of the present invention to provide a method of sealing a terrain surface, such as an irrigation canal, with a waterproof material that is resistant to mechanical damage.
It is another object of this invention to provide a method of sealing the surface of an irrigation canal that is resistant to extreme changes in temperature and that provides a smooth surface for passage of water so that the hydrodynamic characteristics of the canal system are not affected by the sealing method.
It is another object of the invention to provide an apparatus for performing the sealing method on-site.